The Nasa Apollo 10 Mission

The Apollo 10 spacecraft was the second Apollo mission to orbit the Moon,
and the first to travel to the Moon with the full Apollo spacecraft, consisting
of the Command and Service Module (CSM-106, "Charlie Brown")
and the Lunar Module (LM-4, "Snoopy"). The primary objectives
of the mission were to demonstrate crew, space vehicle, and mission support
facilities during a manned lunar mission and to evaluate LM performance
in cislunar and lunar environment. The mission was a full "dry run"
for the Apollo 11 mission, in which all operations except the actual lunar
landing were performed. The flight carried a three man crew: Commander
Thomas P. Stafford, Command Module (CM) Pilot John W. Young, and Lunar
Module (LM) Pilot Eugene A. Cernan.

On 22 May Stafford and Cernan entered the LM and fired the SM reaction
control thrusters to separate the LM from the CSM at 19:36:17 UT. The
LM was put into an orbit to allow low altitude passes over the lunar surface,
the closest approach bringing it to within 14 km of the Moon. All systems
on the LM were tested during the separation including communications,
propulsion, attitude control, and radar. Numerous close-up photographs
of the Moon's surface, in particular the planned Apollo landing sites,
were taken. The LM descent stage was jettisoned into lunar orbit. The
LM and CSM rendezvous and redocking occurred 8 hours after separation
at 03:22 UT on 23 May.

Mission Activities of Apollo 10 included:

A variety of engineering tests were performed, considerable photography
was obtained, and landmark tracking data were gathered to reduce the
size of the landing ellipse for the next space mission. The major activity
for this mission was, of course, the simulated lunar landing with the
lunar module.

Lunar Module Activation - The checkout proceeded smoothly and was
completed in about two hours. The lunar module appeared to be in the
same condition as observed during closeout activity before launch. Transfer
of stowage items and required housekeeping chores were performed. The
transfer from command module to lunar module power was performed without
incident. A landmark tracking training exercise was also performed during
the checkout period.

Lunar Module Operations - The lunar module testing phase of the mission
lasted for more than six hours and involved a number of operations:
the undocking and separation of the lunar module; a series of communications
and radar checks; the firing of the descent engine and moving to within
8 miles of the lunar surface; checking the landing radar over one of
the selected landings sites; and modifying the orbit in preparation
for the return to the command module, staging the lunar module to simulate
an ascent from the lunar surface, and performing the rendezvous with
the command service module.

Landmark Tracking - This was one of the activities planned for the
final day in lunar orbit. Landmark tracking was performed on four landmarks
each revolution for four consecutive revolutions. This activity required
close coordination between the commander, command module pilot, and
the network.

All detailed test objectives were satisfied with the exception of the
lunar module steerable antenna and relay modes for voice and telemetry
communications. Problems with the steerable antenna test objective were
due to the track mode not being switched properly. The communication relay
modes test objectives were not demonstrated due to a lack of time rather
than any problems.

Highlights of the mission include:

Demonstration of color TV camera operating from space.

The second Apollo mission to orbit the Moon.

This was the first time the complete Apollo spacecraft had operated
around the Moon and the second manned flight for the lunar module.

Two Apollo 10 astronauts descended to within eight nautical miles
(14 kilometers) of the Moon's surface, the closest approach ever to
another celestial body to date.

All aspects of Apollo 10 duplicated conditions of the lunar landing
mission as closely as possible in anticipation of a future mission's
landing on the moon.

Apollo 10 was the only Apollo mission to launch from Launch Complex
39B.

The maximum separation between the LM and the CSM during the rendezvous
sequence was about 350 miles (563 km) and provided an extensive checkout
of the LM rendezvous radar as well as the backup VHS ranging device
aboard the CSM, flown for the first time on Apollo 10.